1. Field of the Invention
This invention relates to an outboard motor, particularly to an outboard motor configured for reducing vibration and noise produced during engine operation.
2. Description of the Related Art
Outboard motors equipped with an internal combustion engine for driving a propeller are in wide use. In this type of outboard motor, the engine, which is oriented with its crankshaft parallel to the vertical direction, is mounted directly on the frame of the outboard motor. In the prior art, vibration and noise generated during engine operation is usually reduced by interposing elastic members made of rubber or the like between the outboard motor mounting assembly (mechanism for fastening the outboard motor to a hull (boat)) and the outboard motor proper, as taught, for example, in Japanese Laid-Open Patent Application No. Hei 5(1993)-278684, e.g., paragraphs 0009, 0015, 0016, FIG. 1, etc.
However, when the prior art of inserting elastic members between the outboard motor mounting assembly and the outboard motor proper is adopted, the steering performance of the outboard motor may be degraded if elastic members that are too low in hardness or stiffness (i.e., too soft) are used. Specific problems encountered include degraded response and wandering. The range of selectable elastic member hardness is therefore limited (to ones of a certain level required to avoid steering performance degradation). As a result, outboard motor vibration cannot be sufficiently reduced.
In the prior art, the mounting of the engine directly on the outboard motor frame allows engine vibration to pass to the outboard motor frame, and the resonation of the frame amplifies the vibration and noise of the outboard motor.